1. Field of the Invention
The present invention relates to a power management system, more particularly to a power source management system for managing and powering the powered devices in the PoE (Power over Ethernet) network.
2. Description of the Related Art
Power over Ethernet uses twisted-pair cable to transfer electrical power to several powered devices within an Ethernet network. With this PoE technology, electrical power is supplied to the powered devices, such as IP telephones, wireless LAN access points, network cameras, routers and embedded computers, which is inconvenient to be equipped with a cabled power supply system. In addition, when PoE technology is implemented, the cable structure of the Ethernet does not need to be altered.
The PoE technology uses the IEEE 802.3af/802.3at standard and protocol for supplying power and data to Ethernet. The IEEE standard does not decrease data transmission ability and transmission distance via the network. After assuring the attached device is PoE-compatible, electrical power is supplied to the attached device. When the attached device is non PoE-compatible, electrical power is cut out. Due to these characteristics, the user can combine the conventional power supply device with the PoE-compatible powered device at any desired time and places.
The electrical power supplied by the presently available PoE technology is 48 volt DC, i.e., an electrical power supply mode in high voltage, but with low current. The current is generally below 0.8 amp and the ampere above will be dangerous to the power-supply cable. Currently, an automatic power-supply network for supplying electrical power to factories or worksites generally use 24 volt DC, this current is not suitable to be supplied directly to powered devices in an Ethernet network. Therefore, an improvement should be conducted for PoE technology to be used easily in a worksite power-supply network. In other words, an improvement is required for the powered devices of an Ethernet network.
Therefore, the main object of the present invention is to provide a power management system for managing the power of powered devices in the Power over Ethernet, thereby eliminating the drawbacks encountered in the prior art technology.